\documentclass{report}

\usepackage{fancyhdr}
\usepackage{xepersian}

\fancypagestyle{plain}{%
  \fancyhf{}%
  \fancyhead[L]{\thepage}%
  \fancyfoot[C]{\thepage}%
  \renewcommand{\headrulewidth}{2pt}% Line at the header invisible
  \renewcommand{\footrulewidth}{0.4pt}% Line at the footer visible
}

\begin{document}

\chapter{f}


\end{document}